In recent years, a voice is becoming higher and higher on environmentally friendly electronic products, resulting in great developments of halogen-free technology. On the other hand, with the advent of the lead-free era, besides halogen-free and flame retardant performance for printed circuit board, the property of matching with lead-free soft solder thereof becomes important. Therefore, printed circuit laminates are required on higher thermal resistance and reliability than before. At present the main technique focuses on phosphorus-modified epoxy resin and benzoxazine resin. As is known to all, compared with ordinary epoxy resin, using phosphorus-modified epoxy resin will increase the water absorption of printed circuit laminate, and lower its thermal and moisture resistance.
In order to solve the problem mentioned above, CN101691449A reports that, through synergistic flame retardancy of phenoxyphosphazene compounds and compounds having a dihydrobenzoxazine ring, the flame retardancy was greatly improved. The cured product has high glass transition temperature (Tg), good thermal resistance, high elastic rate, low dielectric dissipation as well as great flame retardancy and processability. However, the thermal resistance of this solution is limited, and its processability is not entirely satisfactory. In addition, CN 101643570A has put forward a halogen-free flame retardant resin composition, and a prepreg, a laminate and a printed circuit laminate made by using the same. The halogen-free flame retardant resin composition comprises: (A) a mixture of phenoxyphosphazene compound (A1) and compound (A2) having a dihydrobenzoxazine ring, 40-80 parts by weight, and the weight ratio of the phenoxyphosphazene compound (A1) and the compound (A2) having a dihydrobenzoxazine ring is 1:10-1:2; (B) a poly epoxy compound, 15-45 parts by weight; (C) a phenolic resin curing agent, 5-25 parts by weight; and (D) an imidazole compound used as curing accelerator, 0.1-1 parts by weight. However, in the technical solution, a lot of compounds having a dihydrobenzoxazine ring are added, the brittleness of the cured product is greater resulting from more addition of the compounds, therefore, the amount of the compounds cannot be too much. In addition, the action of auxiliary curing agent is ignored in the technical solution, making the performance of resin cured product obtained by the solution difficult to be further improved. Accordingly, it becomes a difficult point in the art that how to add a large amount of compounds having a dihydrobenzoxazine ring and make the resin composition achieve better comprehensive properties.